Intake Vacuum Leak

How can you tell you have a vacuum leak on the highway, like what symptoms?


Also, Fel Pro makes an extra thick (almost 1/8") gasket for BBC's. Don't know if they make one for yours?

sealing engines leaks

An old neighbor used to build circle track cars, He would hook up a long vacuum hose from his ranchero to the dipstick tube on his new engines on the stand . then use a stethoscope to listen for leaks. He would then use some gasket sealer and the vacuum would suck in the sealer and stop the leaks.

Intake vacuum leak

55 Tony I don't know about the vacuum leak on the hiway it is after running it hard that the leak starts like on the hiway, It happens after running at about 5-6000 RPMs for a minute or less.

Hmm ... that's all I got.

timothale said:

An old neighbor used to build circle track cars, He would hook up a long vacuum hose from his ranchero to the dipstick tube on his new engines on the stand . then use a stethoscope to listen for leaks. He would then use some gasket sealer and the vacuum would suck in the sealer and stop the leaks.

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That sounds good, but when I had leaks they were always going to the crankcase.

Timothale,

That sounds like a great idea a buddy has a vacuum pump for AC that should work even better. Problem is I don't know what to do about it happening again. The gaskets seal good and everything like I said it only leaks after running at high RPM for a little bit.

I don't know if you re torque you intake or not after a few heat cycles but i always do as my new build I did back in the spring after a few heat cycles I went to re torque and some of the bolts were loose more then i was expecting and nothing bad or to worry about but loose enough that it was off about 5 ftlbs or so. I always torque mine at 25 ftlbs. I would also try and have the engine running and I use a propane torch unlit of course and let it spray around the intake if I ever looked for vacuum leaks or spray with carb cleaner and see if the idle would change.

The best thing is if you have a smoke machine and look for any smoke being sucked in around the intake flange.

86squarebody said:

55 Tony I don't know about the vacuum leak on the hiway it is after running it hard that the leak starts like on the hiway, It happens after running at about 5-6000 RPMs for a minute or less.

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That would be a strange vacuum leak.
In those running conditions your vacuum should be close to zero.
Do you hear something or see something?

Use a straight edge on the intake gasket surfaces and check for warpage. My guess is that the intake it out more than .010"

Greg T said:

Use a straight edge on the intake gasket surfaces and check for warpage. My guess is that the intake it out more than .010"

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Agree with Greg and suspect that the block if not square.

Thanks for all the info guys I will post as to what I find once it is torn down. Should be soon.